Since My Gists only needs to read gists and eventually write gists, limit GitHub API OAuth scope to "gist". Also, have OmniAuth::Strategy skip retrieving user info since it can not be retrieved without "user" GitHub OAuth scope. My Gists only needs login and avatar which are available from the callbacks raw info.
Gist descriptions must be text Character Type
Fix for 'Multiple vulnerabilities in parameter parsing in Action Pack (CVE-2013-0156)'
Not using vendor/plugins, so remove it